Baghouse apparatus



2 Sheets-Sheet 1 Filed Oct. 23 1965 FIG.

INVENTOR.

Wade E. Ballard ATTORNEY Sept- 17, 1968 w. E. BALLARD 3,401,505

BAGHOUSE APPARATUS Filed Oct. 2:5, 1965 2 Sheets-Sheet 2 United States Patent 3,401,505 BAGHOUSE APPARATUS Wade E. Ballard, Rolling Hills, Calif., assignor to Menardi & Company, El Segundo, Caiif., a corporation of California Filed Oct. 23, 1965, Ser. No. 503,731 2 Claims. (Cl. 55-341) ABSTRACT OF THE DISCLOSURE A baghouse construction in which a filter chamber is defined by vertically spaced upper and lower apertured tube plates between which extend open-ended tubular bags of gas-pervious particulate material-arresting fabric connecting corresponding apertures, Each bag is fixed at its upper end to the upper tube sheet and at its lower end releasably fixed to a vertically adjustable thimble section arranged to be releasably locked in telescoping relation to a second thimble section fixed in a corresponding aperture in the lower tube sheet, whereby the bags can be mounted and tensioned by a worker in the filter chamber.

This invention relates to apparatus for baghouses of the type employed for filtering entrained particulate matter from air or other gases, and more particularly to improved means for holding the filter bags within the baghouse in proper position and under suitable tension.

Conventional baghouses include a casing having vertically spaced upper and lower tube sheets respectively provided with registering apertures, between which a corresponding number of filter bags are held in tension. Since the bags are usually made of fragile fibers woven to form a rather delicate fabric, it is not advisable to connect the ends of the filter bags directly to the tube sheets when tensioning the bags because the aperture edges may be sutficiently sharp or rough to tear the fabric. In the interest of extending bag life, it is therefore advisable for each end of a filter bag to be connected to a smooth tubular metal thimble which, in turn, is received in the associated tube sheet aperture. Thus it is the function of the thimbles to hold the filter bags under tension in expanded condition between the tube sheets to thereby resist collapse of the bags. In addition, the establishment of a sealing relationship between the bags and the thimbles prevents the filtered gas from being vitiated by leaking unfiltered gas.

The bags are held in tension because otherwise the fabric would tend to crease or form pleats and folds which would reduce filtering eificiency and tear the fabric, especially if made of glass, or other brittle fiber which breaks easily when bent.

Various thimble constructions have been proposed in the past. At first their main purpose was to line the rough edged apertures of the tube sheets to protect the delicate, woven filter bags from rips and snags either during install-ation or subsequent operation. Thimbles have also been used in the past as adapters to which the ends of the filter bags can be secured, albeit not entirely satisfactorily, as with the aid of an external annular groove in each thimble and an external annular garter spring. As the art progressed, thimbles were also used to apply tension to the filter bags, as by making the lower thimble of heavy construction and slidable in its aperture so as to apply tension to the bag, while effecting a sliding seal with the tube sheet. Still other older arrangements involve the use of an adjustably positioned thimble which is secured to the tube sheet after tension is applied to the filter bag.

As will be seen, the present invention involves the concept of securing the thimbles for each bag to the associated Patented Sept. 17, 1968 tube sheets and to the respective ends of the filter bag, then applying tension to the filter bag and locking the assembly by manipulation of one of the thimbles. With this construction tension may advantageously be applied from within the filter chamber disposed between the tube sheets, rather than from a plenum above the upper tube sheet or from the hopper below the lower tube sheet.

According to the present invention, at least one of the thimbles is constructed of inner and outer tubes in tele scoping relationship with an annular seal between them. One tube is stationary, being secured to the tube sheet in registry with an aperture, One end of the filter bag is connected to the movable tube; and the latter slides or telescopes into the stationary tube to apply tension to the filter bag. Further included are devices which provide interlocking formations on the inner and outer tubes, preferably on opposite sides of the thimble 22, so that by rotation of the movable tube about its axis the tubes can be locked together against axial movement to thereby maintain tension on the filter bag. These interlocking formations may be in the form of a projecting pin on one tube, Which pin is movable along an axially extending slot in the other tube. Serrations, or an axial series of transverse notches, are formed along one side of the slot to receive and grip the pin if moved therein by rotation of the pincarrying tube.

The various objects, features and advantages of the invention will appear more fully from the detailed description which follows, taken in connection with the accompanying drawings forming a part of the present application, and in which:

FIG. 1 is a vertical sectional view of a baghouse incorporating the invention;

FIG. 2 is an enlarged, fragmentary view of the apparatus of FIG. 1;

FIG. 3 is an enlarged view of a fragment of the apparatus of FIG. 1, showing the invention in detail; and

FIG. 4 is a horizontal sectional view, taken along line 44 of FIG. 3.

The baghouse of FIG. 1 is a filtering device having a casing 10 supported on legs 11 and equipped with verti cally spaced upper and lower correspondingly apertured tube sheets 12 and 14, a hopper 16 below the lower tube sheet 14, an upper plenum 18 above the upper tube sheet 12, and an inlet duct 19 above the upper plenum 18. A plurality of vertically elongated, tubular filter bags 20, extending between vertically aligned, corresponding apertures in the respective tube sheets 12 and 14, are each held between upper and lower thimbles 21 and 22.

An inlet damper 23 controls the flow of dirty gas from the inlet duct 19 to the upper plenum 18. A door 24 closes a manhole in the casing 10 and provides access for workmen from an upper platform 26 to the upper plenum 18, and another normally closed door 28 provides similar access from a lower platform 30 to a vertically elongated filter chamber 32 between the tube sheets 12 and 14.

During normal filtering operation, with inlet damper 23 open as shown in FIG. 1, dirty gas flows from duct 19 through plenum 18, and into the open upper ends of the filter bags 20, as indicated by the arrows. Next the dirty gas flows lengthwise of the bags 20 and clean filtered gas exits through the bag walls, thereafter flowing from the filter chamber 32 through the open exhaust damper 34 into the exhaust duct 36, from whence the clean, filtered gas is either delivered to a point of use or discharged to the atmosphere via a stack (not shown). Some of the particulate matter separated from the dirty gas clings to the inner surface of the bag walls, but in the main it is deposited in the bottom of the hopper 16 and carried away by a screw conveyor 42. During the filtering operation, a deflation duct 38 having an inlet in the hopper 16 is closed by a deflation damper 40, when positioned as shown in solid lines.

However, during the cleaning operation when particulate matter is removed from the inner surface of the filter bags 20, the inlet damper 23 and the deflation damper 40 are moved to the positions illustrated with broken lines in FIG. 1 so that inlet damper 23 is closed and deflation damper 40 is open, while exhaust damper 34 remains open in a suitable position. With dampers thus positioned, a fan 45 or other suitable gas translating apparatus is operated to draw clean gas from the exhaust duct 36, through damper 34, into the filter chamber 32 for flow first through the walls of the filter bags 20, next into the hopper 16, and then through the damper 40 and out the deflation duct 38, for delivery to the inlet duct 19 Wh r in preference to discharging the now dirty gas to the atmosphere, the dirty gas can be directed for cleaning into the upper plenum of a separately compartmented, companion filter chamber in the same baghouse which is connected to the common inlet duct 19 and the common exhaust duct 36. In this way clean gas from a filter chamber set for filtering operation is available for back flow through a filter chamber set for cleaning of its bags, all by suitable positioning of their respective dampers 23, 34 and 40.

Although not so limited, the invention is especially applicable to filtering devices employing tubular filter bags 20 woven of fiberglass or other heat resistant ceramic material and which may be open at both ends. Fiberglass can withstand temperatures up to 600 P. so that gases at such a temperature can be introduced directly to the filter chamber 32, quite unlike the situation when filter bags of other known synthetic materials, such as Dacron, are employed. With the synthetic materials, having temperature capabilities of about 300 F., it is sometimes necessary to employ apparatus and procedure for the preliminary step of reducing the temperature of the gas to be filtered to below the temperature capability of the filter bag material, all because others are unable to obtain satisfactory service life from the more delicate fiberglass filter bags. The other parts of the apparatus may be made of metal, preferably steel.

Recognizing that fiberglass filter bags 20 are easily torn when pleated or sharply bent, the present invention provides means for securing the filter bags 20 gently and under tension in order to avoid bruises and sharp bends, of which the latter may be occasioned by the formation of pleats or creases, as during normal cleaning operation. Furthermore, by preventing the formation of pleats and creases, the filtering effectiveness of the bags is improved.

The apparatus shown in FIG. 1 employs a vertically spaced series of anti-collapse rings 44 loosely disposed within each filter bag 20 and carried on a longitudinally extending rod or cable 46 depending from an upper support 48.

The present invention provides means for tensioning the filter bags 20 from within the filter chamber 32 and specifically eliminates any need to enter the upper plenum 18 or the hopper 16. Only one workman is required to effect tensioning of a bag during either installation or replacement of the filter bags 20.

In the drawings, the upper and lower thimbles 21 and 22 are of different construction, since it is the lower thimble 22 that is employed both to hold the filter bag and apply adjustable tension, while the upper thimble 21 simply serves to hold the filter bag while resisting tensioning forces and therefore can be of simple construction.

Referring now to FIG. 2, the upper thimble 21 comprises a tubular body portion 54 having an outwardly flared flange 56 which seats on top of tube sheet 12 and thus supports the thimble 21. At the lower end of the upper thimble 21 there is formed an inwardly extending rim or lip 60 which serves as a ledge for holding the upper end for the filter bag 20 against downward movement. It will be noted that both ends of the filter bag 20 are provided with a hem in which is received a ring 62, preferably of stainless steel material, sewn or otherwise secured in place to provide circular form to the ends of the filter bag 20 and also, in the case of the upper end of the filter bag, to engage the rim or lip 60 of the upper thimble 21. With this arrangement the upper endof the filter bag 20 is open to receive gases to be filtered, and it is supported and retained against downward movement by the inturned rim 60, even when a tensioning force is applied at the lower end of the bag.

The lower thimble 22 is an assembly which serves to connect the lower end of the filter bag 20 to the lower tube sheet 14 and also to apply tension to the bag at the lower end thereof. The lower thimble 22 comprises inner and outer tubes 64 and 66 in telescoping relationship formed about the longitudinal axis of the bag 20. Stated another way, one of the tubes is slidably received within the other and is relatively movable by rotation about the axis or linearly in axial direction. As shown in FIGS. 3 and 4, the inner tube 64 is somewhat similar in construction to the upper thimble 21, since it includes an annular flange 68 which is peened after installation so that it flares outwardly to cooperate with an outwardly extending annular projection 70 at the lower end of a generally cylindrical body portion 72 for gripping the portion of the lower tube sheet 14 rimming the aperture through which it extends, and thereby securing the inner tube 64 stationary with respect to the lower tube sheet 14. Optionally the lower end of the tube 64 can be welded to the lower tube sheet 14, as from a position inside the filter chamber 32, instead of peening the fiange 68. Formed in the upper end of the inner tube 64 is an external annular groove 74 receiving a seal ring 76, preferably of resilient material resistant to heat and chemical attack, the purpose of which is to maintain the inner and outer tubes 64 and 66 in sealing relationship in all relative positions thereof.

At the upper end of the outer tube 66 is formed an inturned rim or annular lip which, like the inturned lip 60 of the upper thimble 21, serves as a retaining ledge for the lower end of the filter bag 20 by engaging the ring 62 within its lower hem to thereby provide a positive stop against upward movement of the lower end of the filter bag 20 when the bag is tensioned. A pair of handles 82 are attached on the outer surface of the outer tube 66 for convenience in manually manipulating the outer tube.

The lower thimble assembly 22 is provided with a ratchet and pin device to facilitate interlocking the inner and outer tubes 64 and 66. Broadly stated, it is the function of the interlock device to permit the inner and outer tubes 64 and 66 to be telescoped, or moved in axial direction relative to each other, in order to apply tension to the filter bag 20, as by moving the outer tube 66 axially downwardly. Then, after the desired tension has been applied to the filter bag 20, the outer tube 66 may be rotated relative the inner tube 64 in order to lock the outer tube 66 against axial movement, with the result that the tension applied to the bag is maintained. As best seen in FIG. 3, the preferred form of interlock comprises axially elongated slots 84 formed at diametrically opposite locations in the outer tube 66, with an axial series of transverse notches 86 along one edge of each slot 84. The slots 84 and the notches 86 receive and cooperate with corresponding outwardly extending pins 88 on the inner tube 64 to secure the lower thimble against axial movement when the pin 88 is received in one of the notches 86.

-It is to be understood that the positions and function of the inner and outer tubes 64 and 66 may be transposed; and, likewise, either tube may have the slots 84 and the other pins 88, in practicing the invention.

To install a filter bag 20 in the position shown in FIG. 1, the upper end of the filter bag is first secured to the upper thimble 21 by seating the upper end of the bag and its ring 62 against the upper surface of the inturned rim 60. The lower thimble 22, which is in vertical alignment with the upper thimble 21, is then made ready for reception of the lower end of the filter bag by rotating the outer tube 66 either until the pins 88 if free of the notches 86 or the outer tube 66 is in an elevated position. Next, the lower end of the filter bag 20 and its ring 62' are seated against the lower surface of the inturned rim 80. The desired tension is then applied to the bag 20 by applying equal downward force to the handles 82, with the pins 88 free to slide upwardly in the slot 84 as the outer tube 66 is pressed downwardly in telescoping relation to the inner or stationary tube 64. The lower thimble 22 is then locked, with the selectively applied tension maintained substantially constant, by simply rotating the outer tube 66 so that each pin 88 is received in a selected one of the notches 36. With a suitable angular inclination of each of the notches 86, the pins 88 may be held captive until the outer tube 66 is rotated in opposite direction, after which the pins 88 are released for free sliding movement in the slot 84. Manual manipulation of the outer tube 66 may be performed by a workman standing in the filter chamber 32 on the lower tube sheet 14.

Although the invention has been shown specifically it will be obvious to those familiar with the art that it is not so limited, but it is susceptible of various changes and modifications without departing from the spirit thereof, as covered by the claims which follow.

What is claimed is:

1. A filtering device comprising:

a casing having a gas inlet and outlet,

upper and lower spaced apart tube sheets within said casing provided with a plurality of corresponding vertically aligned apertures and defining with said casing a filter chamber communicating with said gas inlet and outlet,

a plurality of fiberglass filter bags of axially elongated tubular construction in said filter chamber extending between respective corresponding apertures of said tube sheets for filtering particulate matter from gases fiowim through said casing,

means including first and second thimbles attached to said upper and lower tube sheets respectively for securing opposite ends of each filter bag to the respective upper and lower tube sheets under tension between them and in registry with corresponding apertures in said tube sheets,

an inner tube fixedly mounted in its corresponding aperture and extending into the space between said tube sheets, means for adjustably tensioning said filter bag comprising an outer tube having one end secured to the respective end of its respective bag and its other end surrounding and in telescoping relation with said inner tube, a sealing ring positioned between the telescoping portions of said inner and outer tubes,

one of said tubes having an axially elongated slot with an axial series of transverse notches formed therein, and a locking member on the other of said tubes received in said slot and axially movable therein incident to movement of said second tube relative to said first tube, said locking member being adapted for reception in one of said notches upon relative rotational movement of said tubes about said axis for securing said tubes against relative axial movement,

the construction and arrangement being such that said filter bag is placed in tension by relative movement of said tubes in one axial direction and said tubes are locked against relative axial movement and said filter bag is maintained in tension 'by relative movement of said tubes in one direction of rotation. 2. In a baghouse for filtering particulate material from a gas, a pair of vertically spaced horizontally arranged upper and lower apertured tube sheets arranged to define the top and bottom of a filter chamber therebetween, an open-ended tubular filter bag of gas-pervious particulate materialarresting fabric arranged to connect corresponding vertically aligned apertures in said tube sheets, a thimble seated in an aperture in the upper tube sheet, means for holding the upper end of said filter bag in said thimble against downward movement, a lower thimble assembly comprising an inner tube having its lower end fixedly mounted in the corresponding aperture in said lower tube sheet and projecting upwardly therefrom towards said upper tube sheet, and means for adjustably tensioning said filter bag from within said filter chamber comprising an outer tube in said lower thimble assembly having its upper end secured to the lower end of said filter bag and its lower portion surrounding and in telescoping relation with the upwardly projecting portion of said inner tube, a sealing ring positioned between the telescoping portions of said inner and outer tubes, and means above the level of said lower tube sheet for releasably interlocking the telescoping portions of said inner and outer tubes by relative axial and rotational movement of said tubes to hold said bag in its desired tensioned position comprising one of said tubes having an axially elongated slot with an axial series of transverse notches formed therein, and a locking member on the other of said tubes received in said slot and axially movable therein incident to movement of said other of said tubes, said locking member being adapted for reception in one of said notches upon relative rotational movement of said tubes about said axis for securing said tubes against relative axial movement.

References Cited UNlTED STATES PATENTS 219,098 9/1879 Jewell 285-303 X 469,005 2/1892 Anderson 285-303 X 503,818 8/1893 Watt 285-303 X 747,379 12/1903 Connelly et al 285-303 825,810 7/1906 Cooke 285303 X 1,232,436 7/ 1917 Scritchfield 285-303 1,703,681 2/1929 Miller 55-341 X 1,813,896 7/1931 Paine 55378 X 1,898,759 2/1933 Burt. 2,005,690 6/1935 Hertz 55374 2,143,664 1/ 1939 Snyder. 2,612,236 9/1952 Vedder. 2,805,731 9/1957 Kron 55--341 X 2,805,732 9/1957 Martinez 55430 X 2,875,847 3/1959 Pring 55-341 X 3,166,392 1/1965 Keaton 55--341 X 3,170,777 2/ 1965 Held. 3,177,636 4/1965 Jensen 55341 FOREIGN PATENTS 48,434 11/1937 France. 1,374,945 10/ 1964 France.

564,921 10/ 1944 Great Britain.

HARRY B. THORNTON, Primary Examiner.

D. TALBERT, A ssz'stant Examiner. 

